The present invention relates to a ligation device used in an endoscopic surgery, for tying up (ligating) a bleeding part of a mucous membrane of a human body cavity.
Conventionally, a ligation device includes a cylindrical hood which is mounted to a tip of an insertion tube of an endoscope. The hood is so constituted that the hood projects (in a inserting direction) from the tip of the insertion tube. The insertion tube has a suction channel which opens at an end surface of the tip of the insertion tube. When the hood is mounted to the insertion tube, the suction opening is surrounded by the hood.
An elastic ring is used as a ligature, that is, a member which ties up the mucous membrane. The ring is made of rubber or the like, and is mounted to an outer surface of the hood in such a manner that the ring is elastically extended. In order to push the ring out of the hood toward the mucous membrane, a movable sleeve is provided to the outer surface of the hood. The movable sleeve is slidable in the axial direction of the hood.
On ligating a mucous membrane, an operator inserts the insertion tube into the human body cavity so that the hood abuts the mucous membrane. Then, the operator starts a suction (via the suction opening), so that the mucous membrane is sucked in a hood. With this, the sucked mucous membrane forms a polyp. Further, the operator actuates the movable sleeve thereby to push the ring out of the hood, so that the ring surrounds the polyp. Once the ring surrounds the polyp, the ring is contracted due to its elasticity. With this, the polyp is tied up by the ring.
However, since the ring is conventionally provided to the outer surface of the hood, the diameter of the ring must be relatively large. Thus, it is difficult to ligate a small part such as micro blood vessels.
Further, the insertion tube has a view window which enables an operator to observe a mucous membrane. The view window is provided at an end surface of the insertion tube. However, when a suction is performed, the mucous membrane is sucked in the hood and interferes the view of the operator. That is, it is difficult for the operator to observe the mucous membrane during the ligation.